1. Field of the Invention
The present invention relates to an image processing method, an image processing device, and an image capturing device.
2. Description of the Related Art
Recently, the demand of a wide angle image capturing device has increased for the application to a back-monitor of a car and the like. However, because the magnification chromatic aberration or distortion increases with increasing the view angle and it is difficult to design an optical system with a small aberration, it may be necessary to combine it with image processing so as to improve the performance.
As a conventional aberration correction technique in an image capturing device using an optical system with a certain magnification chromatic aberration or distortion, there is provided a method for applying a coordinate transformation to R (red), G (green) and B (blue) signals obtained by an image capturing device such as a CCD or a CMOS sensor, independently for each RGB color component at a subsequent stage, so that the magnification chromatic aberration and the distortion are corrected simultaneously, or a method for applying a coordinate transformation to all the RGB color components while the ignoring magnification chromatic aberration, so that only the distortion is corrected (for example, see JP-A-2006-345054.).
In the conventional method for applying a coordinate transformation to each RGB color component independently to correct the magnification chromatic aberration and the distortion simultaneously, a memory with a large capacity and a small latency at the time of random access, such as an SRAM, or a multi-port memory is needed for each RGB color component. However, a large capacity SRAM or a memory having plural ports is very expensive, and accordingly, the price of the device has been very high, particularly, in the case of a high resolution which requires a large capacity.
Meanwhile, the method for applying a common coordinate transformation to each RGB color component to correct only the distortion requires a large capacity memory and it may be possible to use a DRAM or the like in which the price of one chip or component is low but is not available if the magnification chromatic aberration is hardly ignored at a wide view angle.
Whereas the distortion is homogeneous over all of the RGB color components, the magnification chromatic aberration is different among the color components. Furthermore, the magnification chromatic aberration is smaller than the distortion. Therefore, it is preferable to correct the magnification chromatic aberration and the distortion separately.
Meanwhile, an independent correction circuit for each color component is commonly needed for correction of a magnification chromatic aberration and it may be necessary to correct the magnification chromatic aberration at the minimum circuit scale for cost reduction.